Coolers are widely used. A myriad of applications call for maintaining temperatures at a reduced level. Some examples include food processing plants, dairies, bakeries, bottling plants, restaurants, supermarkets, hospitals, and school cafeterias. In the medical setting, coolers are used to maintain the temperature of test samples and medications. In the restaurant business, coolers are used to keep food items, beverages etc. at certain temperatures. The refrigerated compartment of such coolers may be kept below 32° F. Hence, coolers are often referred to as refrigerator or freezers. In commercial settings, coolers are often large enough for a person to walk into. The contents of the cooler are frequently accessed, hence the doors of the coolers are opened frequently.
Every time the cooler door is opened, not only does a draft of cool air escape out of the cooler via the cooler's doorway, but a draft of warm air also enters the cooler. This infiltration of ambient warm air into the refrigerated compartment while the cooler door is open invariably results in raising the interior temperature of the refrigerated compartment of the cooler. This may overload the refrigeration system used to keep the temperature at a desired set point, and ultimately results in the refrigeration system consuming more power to maintain the internal cooler temperature. Furthermore, the food industry has a keen interest in controlling the damaging effect of losing cool air, because food will start to spoil if the temperature inside the cooler is not maintained at the proper temperature.
Keeping the door closed is one way to avoid air infiltration. But opening the door is inevitable. Hence a solution is needed for retaining the cool air within the cooler.
An air curtain is a device that provides a barrier that reduces the airflow through an open refrigerator or freezer doorway, yet at the same time allows a person to pass through the doorway. The air curtain is a layer or curtain of air that is formed by a blower emitting a stream of air. Air curtains became increasingly popular in Europe throughout the late 1940's and 1950's. The reason for the wide spread use and popularity of air curtains lies in the array of advantages offered by the air curtain. The air curtain aids in maintaining the cooler's temperature by retaining the cool air within the refrigerated compartment, hence reducing the energy costs.
The air curtain serves a twofold purpose of retaining the cooler air within the cooler and reducing the amount of warm air that enters through the cooler's open door. It must be noted that the air curtain does not completely prevent cold air from escaping and warm air from entering via an open door. However, the air curtain reduces the amount of cold air that escapes the cooler and the amount of warm air entering the cooler.
Conventional air curtains are sized to cover the entire doorway area, and generally have a vertical flow of air. Air curtains are also available in different forms, such as continuously running air curtains, temperature activated air curtains, and air curtains equipped with a control panel that allows the user to preset a configuration of the control parameters of the air curtain such as humidity, air speed and velocity etc.
One problem with prior art air curtain devices is that they are neither effective nor efficient when used for applications such as walk-in coolers. If the power consumed by the device that generates the air curtain is greater than the savings in power consumption due to inhibited air flow through an open doorway, the air curtain device is not worth using. Also, if the initial cost of the device is too high, the cost savings from the power savings over the life of the device may not pay for the device. Another problem is that many air curtain devices are large or bulky, and take up precious space inside the cooler, particularly with ductwork. Many times there is not room to install an overhead air curtain on either the inside or outside of a walk-in cooler. Many prior art air curtain devices have adjustable nozzle directions and fan speeds. However, most people cannot make proper adjustment to achieve satisfactory results.
Thus there is a need for an air curtain device that can be used for walk-in coolers and that is fairly inexpensive to build, is compact and decreases the total power consumption of the cooler, taking into account the added power consumption of the air curtain device. It is preferably if such a device does not need the user to make adjustments.